You will see the Character Map window below:
(notice the keystroke suggestion in the bottom right corner)

You can use the ALT-key combination suggested, or you can pick the character you want, hit the "Select" button and it will put it in the "Characters to copy:" space. Then you can simply hit the "Copy" button and return to wherever you are typing and paste the selected Character.

Jon, those would most likely have to be added to drawings as actual "symbols", not entered within character text typing. Without finding and using entirely a new font (for the entire Revit project), that has those characters in them, there is no way that I know of to have these symbols be typed as text.